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Question 1206388: Which quadratic function in vertex from can be represented by the graph that has the vertex at (0, -4) and passes through the point (3, -7)?
A. y = -1/3x^2 - 4
B. y = 1/3(x + 4)^2
C. y = 1/3x^2 - 4
D. y = -1/3(x + 4)^2
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850)   (Show Source):
You can put this solution on YOUR website!
Which quadratic function in vertex from can be represented by the graph that has
the vertex at ( ,  ) => , 
passes through the point ( , )=( , )=> ,
use vertex form formula
 ...substitute given ,
, ,
go to
...substitute , ,
answer: A
Answer by ikleyn(52817)  (Show Source):
You can put this solution on YOUR website! .
Which quadratic function in vertex from can be represented by the graph
that has the vertex at (0, -4) and passes through the point (3, -7)?
A. y = -1/3x^2 - 4
B. y = 1/3(x + 4)^2
C. y = 1/3x^2 - 4
D. y = -1/3(x + 4)^2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This problem is not to make long calculations.
It is to be solved MENTALLY in your head, giving a correct answer in one second.
The word "Which" in the question means "find/identify one in the list".
The vertext at (0,-4) means that the choice is between (A) and (C),
since (B) and (D) have vertex at x = -4.
Looking at the point (3,-7) , you see that it lies BELOW the level y= -4;
hence, the parabola must be opened downward.
It implies that the ANSWER is (A).
For reability, you can check it: y =  =  = -3 -4 = -7. ! correct !
Solved.
Once again: the point of this task is to provide a correct answer quicker than you blink an eye.
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